The invention relates to a method for coating a substrate with a calcium phosphate layer.
The plasma spray method is used to coat substrates in particular with a bioactive calcium phosphate layer, e.g. hydroxyapatite. However, this method is unsuitable if the substrate consists of small particles or is not resistant to heat. Electrochemical deposition of calcium phosphate is likewise inapplicable to particles even if the particles are electrically conducting.
U.S. Pat. No. 6,153,266 describes a method for producing a calcium phosphate layer, in which in a first step the substrate is immersed in a phosphate-containing bath which contains no calcium. The substrate is subsequently removed from the solution, dried and immersed in a second solution which has a ph of 8 and contains calcium. Calcium phosphate is formed on the surface of the substrate in this solution. The first disadvantage of this method is that the coating is carried out with 2 method steps. A further disadvantage is that it is not possible with the 2-step method to produce the layer thickness in the desired scope. For thick layers, therefore, the known method provides a further method step in which the substrate provided with the calcium phosphate layer is immersed in a calcium phosphate solution.